Wing tip device

ABSTRACT

A wing tip device having a first wing tip device element for attaching at a first wing tip device element root to a tip of an aircraft wing, and a second wing tip device element extending from a second wing tip device element root to a second wing tip device element tip, the second wing tip device element root outboard, when viewed in the wing planform direction, of the first wing tip device element root; the first wing tip device element having a first wing tip device element leading edge and a first wing tip device element trailing edge, and the second wing tip device element having a second wing tip device element leading edge and a second wing tip device element trailing edge; and a fairing between the first and second wing tip device element which extends aft from the second wing tip device element trailing edge.

RELATED APPLICATION

This application claims priority to United Kingdom GB ApplicationNumber: GB 1815357.7 filed Sep. 20, 2018, the entirety of which isincorporated by reference.

FIELD OF THE INVENTION

The present invention relates to a wing tip device, a wing including thewing tip device, an aircraft including the wing, and a method ofattaching a wing tip device.

BACKGROUND OF THE INVENTION

Interference effects between two objects in an airflow can be createdwhen the wetted surfaces of those objects are in close proximity. Forexample, interference effects exist between an aircraft's fuselage andits wings. These effects can be particularly pronounced on wing tipdevices with multiple lifting surfaces, such as split winglets, due toboth surfaces generating lift and the sharp intersection of a downlethaving horseshoe vortex interference effects.

At the rearward junction of these lifting elements, adverse pressuregradients are present from the two lifting surfaces, the combination ofwhich can cause excessive boundary layer growth and increased drag. Ifthese effects could be minimised, the benefits would be appreciable.

SUMMARY OF THE INVENTION

According to an aspect of the invention, there is provided a wing tipdevice having a first wing tip device element for attaching at a firstwing tip device element root to a tip of an aircraft wing, and a secondwing tip device element extending from a second wing tip device elementroot to a second wing tip device element tip, the second wing tip deviceelement root outboard, when viewed in the wing planform direction, ofthe first wing tip device element root; the first wing tip deviceelement having a first wing tip device element leading edge and a firstwing tip device element trailing edge, and the second wing tip deviceelement having a second wing tip device element leading edge and asecond wing tip device element trailing edge; and a fairing between thefirst and second wing tip device element which extends aft from thesecond wing tip device element trailing edge.

A wing tip device is a wing-like element that extends from the wing tipof an aircraft. A split winglet is a particular example that includes awing-like lifting surface projecting upwardly (an ‘uplet’) from thewing, and a wing-like lifting surface projecting downwardly (a‘downlet’) from the wing.

A fairing is an external structure added to smooth the outline betweenrespective surfaces, increase aerodynamic streamlining, and reduce drag.

The wing planform direction is the direction normal to the plane of thewing.

By placing the fairing between the first and second wing tip deviceelements, the interference effects and vortical flow in the junctionbetween the wing tip device elements can be reduced, thereby reducingdrag, especially at high speed. Extending the fairing to project aftfrom the trailing edge of the second wing tip device element mitigatesthe adverse pressure gradients so that boundary layer growth and dragare both reduced.

According to a second aspect of the invention, there is provided anaircraft wing, comprising a root end and a tip end, and a wing tipdevice according to the first aspect attached to the tip end.

According to a third aspect of the invention, there is provided a fixedwing aircraft, comprising a wing according to the second aspect.

According to a further aspect of the invention, there is provided amethod of assembling a wing tip device, the wing tip device including: afirst wing tip device element with a first wing tip device element rootend for attaching to an aircraft wing and a first wing tip deviceelement trailing edge, a second wing tip device element having a secondwing tip device element root end and a second wing tip device elementtrailing edge, and a fairing; the method comprising the steps of:attaching the second wing tip device element root end to the first wingtip device element outboard of the first wing tip device element rootend, and attaching the fairing between the first and second wing tipdevice element which extends aft from the second wing tip device elementtrailing edge.

The second wing tip device element trailing edge may be forward of thefirst wing tip device element trailing edge

The fairing may extend to the first wing tip device element trailingedge.

The fairing may extend aft of the first wing tip device element trailingedge.

The fairing may be separable from the first wing tip device elementand/or the second wing tip device element. The fairing may be integrallyformed with the first wing tip device element or second wing tip deviceelement so that the respective wing tip device element can be built as asingle molding.

The leading edge of second wing tip device element may be at or inboardof the leading edge of the first wing tip device element.

The fairing may extend forward of the second wing tip device elementtrailing edge. The presence of a horseshoe vortex in the junctionadjacent the leading edge of the second wing tip device element can beexacerbated further aft. By providing a fairing adjacent to and forwardof the leading edge of the second wing tip device element, these effectscan be reduced and the associated increases in drag mitigated.

The wing tip device may have a vertex between the second wing tip deviceelement and the first wing tip device element, when viewed in theaircraft longitudinal direction, the vertex having an angle of less than120 degrees. The vertex angle may be less than 105 degrees or less than90 degrees.

The aircraft longitudinal direction is the direction along an axisbetween the nose end and tail end of the aircraft fuselage.

The fairing may have a width extending across the first wing tip deviceelement substantially in the thickness direction of the second wing tipdevice element, and wherein the width is least 15% of the root thicknessof the second wing tip device element and/or no more than 100% of theroot thickness of the second wing tip device element, such as a widththat is at least 25% of the root thickness of the second wing tip deviceelement.

The first wing tip device element has a wetted area, and the second wingtip device element has a wetted area, and wherein the wetted area of thesecond wing tip device element may be larger than the wetted area of thefirst wing tip device element. The wetted area of the second wing tipdevice element may be less than 20% of the wetted area of the first wingtip device element.

The wetted area of a device is the area of that device that is exposedto the external airflow.

The fairing may extend to the leading edge of the second wing tip deviceelement along an upper aerodynamic surface of the second wing tip deviceelement.

The fairing may extend towards the leading edge of the second wing tipdevice element along an upper aerodynamic surface and/or a loweraerodynamic surface of the second wing tip device element.

The fairing may extend around the leading edge of the second wing tipdevice between the upper and lower aerodynamic surface areas.

An avionic system or light may be attached to the fairing at a positionaft of the first wing tip device element trailing edge. The avionicsystem may be attached at the cusp. The avionic system may be a sensor,an antenna, or any other suitable avionic device known in the art.

Avionic systems are electronic systems used on aircraft, for instancesystems used for navigation and communication.

The first wing tip device element may be an upwardly extending wing tipdevice element. The second wing tip device element may be a downwardlyextending wing tip device element. The first wing tip device element maybe a downwardly extending wing tip device element. The second wing tipdevice element may be an upwardly extending wing tip device element.

The fairing may form an angle of less than 40 degrees to the firstand/or second wing tip device element at an intersection of the fairingto the respective wing tip device element.

The fairing may have a concave outer surface, when viewed in theaircraft longitudinal direction, between the first wing tip deviceelement and second wing tip device element.

The fairing may enclose a hollow volume.

One or more fasteners may be disposed between the fairing and the firstwing tip device element or second wing tip device element.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described with reference to theaccompanying drawings, in which:

FIG. 1 is a plan view of an aircraft;

FIG. 2 shows a wing tip device viewed along the aircraft longitudinalaxis;

FIG. 3 shows a perspective view of the wing tip device;

FIG. 4 shows the wing tip device including a fairing according to afirst example;

FIG. 5 shows a perspective view of the wing tip device including afairing according to a first example;

FIG. 6 shows a close-up view of the trailing edges of the first andsecond wing tip device elements of the wing tip device.

FIG. 7 shows the wing tip device including the fairing viewed along theaircraft longitudinal axis;

FIGS. 8a-b show a second example of the wing tip device including afairing extending to the trailing edge of the first wing tip deviceelement;

FIG. 9 shows a third example of the wing tip device including a fairingextending aft of the trailing edge of the first wing tip device element;

FIG. 10 shows a fourth example of the wing tip device including afairing with an avionic system attached;

FIG. 11 shows a fourth example of the wing tip device including afairing;

FIG. 12 shows a fifth example of the wing tip device including afairing;

FIG. 13 shows a further example of the wing tip device including afairing extending adjacent the upper surface of the second wing tipdevice element;

FIG. 14 shows further example of the wing tip device including a fairingextending adjacent the lower surface of the second wing tip deviceelement;

FIGS. 15-16 show further examples of the wing tip device in which thefirst wing tip device element is a downwardly extending wing tip deviceelement and the second wing tip device element is an upwardly extendingwing tip device element.

DETAILED DESCRIPTION OF EMBODIMENT(S)

FIG. 1 shows an existing aircraft 1 with port and starboard fixed wings2, 3, engines 9, a fuselage 4 with a nose end 5 and a tail end 6, thetail end 6 including horizontal and vertical stabilising surfaces 7, 8.The aircraft 1 is a typical jet passenger transonic transport aircraftbut the invention is applicable to a wide variety of fixed wing aircrafttypes, including commercial, military, passenger, cargo, jet, propeller,general aviation, etc. with any number of engines attached to the wingsor fuselage.

Each wing 2, 3 of the aircraft 1 has a cantilevered structure with alength extending in a span-wise direction from a root to a tip, the rootbeing joined to the aircraft fuselage 4. At the tip of each wing 2, 3 isa wing tip device 12 outboard of a main wing portion 10. The wings 2, 3are aft swept and have a number of flight control surfaces.

As the wings 2, 3 are similar in construction, only the wing tip device12 of the starboard wing 3 will be described in detail with reference toFIG. 2.

The wind tip device 12 includes a first wing tip device element 20 whichis an upwardly extending wing tip device element, and a second wing tipdevice element 30 which is a downwardly extending wing tip deviceelement. The first wing tip device element 20 includes an upperaerodynamic surface 23, a lower aerodynamic surface 24, a root end 21which is attached to the outboard end of the main wing portion 10, and atip end 22 extending from the root end 21 in a generally spanwisedirection, with reference to a plane of the wing, such that the firstwing tip device element 20 increases the wingspan of the aircraft 1. Thecant angle of the first wing tip device element 20 is increased incomparison to the wing 3 and continues to increase from the root end 21of the first wing tip device element 20 to the tip end 22 of the firstwing tip device element 20. Note that the term cant angle is defined asthe angle between the wing tip device elements 20, 30 and a referenceplane of the wing 3.

The second wing tip device element 30 has an upper aerodynamic surface33, a lower aerodynamic surface 34, a root end 31 attached to the loweraerodynamic surface 24 of the first wing tip device element 20 outboardof the root end 21 of the first wing tip device element and inboard ofthe tip end 22 of the first wing tip device element. The second wing tipdevice element 30 extends at an angle of approximately 90° to the firstwing tip device element 20. The tangential angle between the first wingtip device element 20 and the second wing tip device element 30 causesinterference affects between the respective surfaces, for examplebetween the lower aerodynamic surface 24 of the first wing tip deviceelement 20 and the upper aerodynamic surface 33 of the second wing tipdevice element 30.

As shown in FIG. 3, the second wing tip device element 30 is positionedon the lower aerodynamic surface 24 of the first wing tip device element20 between the leading edge 26 and trailing edge 25 of the first wingtip device element 20, such that the leading edge of the second wing tipdevice element 30 is aft of the leading edge of 26 of the first wing tipdevice element and the trailing edge 35 of the second wing tip deviceelement 30 is forward of the trailing edge 25 of the first wing tipdevice element 20. To reduce the drag across this junction, a fairing 40is included that contours between the respective surfaces of the firstwing tip device element 20 and the second wing tip device element 30.The fairing 40 encloses a hollow volume defined between the outersurface of the fairing, and the first and second wing tip device element20, 30. The fairing 40 is attached to the first and second wing tipdevice elements 20, 30 by fasteners (not shown) within the hollow volumeof the fairing 40 and hidden from the external airflow by the fairing.The fairing may alternatively be solid, or porous, and recesses made inthe internal volume of the fairing 40 if fasteners project from thesurfaces of the first and/or second wing tip device elements 20, 30. Thefairing 40 wraps all the way around (i.e. entirely surrounds) the secondwing tip device element 30 at the root end 31 to envelope the junctionbetween the second wing tip device element 30 and the first wing tipdevice element 20.

As shown in figures in 5-7 the fairing 40 is contoured between the upperaerodynamic surface 33 of the second wing tip device element 30 and thelower aerodynamic surface 23 of the first wing tip device element 20,between the lower aerodynamic surface 34 of the second wing tip deviceelement 30 and the lower aerodynamic surface 24 of the first wing tipdevice element 20, forward of the leading edge 36 of the second wing tipdevice element 30 towards the leading edge 26 of the first wing tipdevice element 20, and between the trailing edge 36 of the second wingtip device element 30 and the trailing edge 25 of the first wing tipdevice element 20. The outer surface of the fairing 40 is concave so asto create a smooth aerodynamic profile at the junction of the first wingtip device element 20 and second wing tip device element 30 to reduceinterference effects.

As shown in FIG. 7, the fairing 40 forms a first angle 41 ofapproximately 15° at an intersection of the fairing to the outer surfaceof the first wing tip device element 20 and a second angle 42 of betweenapproximately 7° and 30°, such as 15° at an intersection of the fairingto the outer surface of the second wing tip device element 30. Thefairing 40 has a first upper width 43 extending in a directionsubstantially perpendicular to the chordwise direction of the first wingtip device element 20 extending across the thickness of the first wingtip device element 20 from the upper aerodynamic surface 33 of thesecond wing tip device element 30, a first lower width 44 extending in adirection substantially perpendicular to the chordwise direction of thefirst wing tip device element 20 from the lower aerodynamic surface 34of the second wing tip device element 30, a second upper width 45extending in a direction substantially perpendicular to the chordwisedirection of the second wing tip device element 30 across the thicknessof the upper aerodynamic surface 33 of the second wing tip deviceelement 30, and a second lower width 46 extending in a directionsubstantially perpendicular to the chordwise direction of the secondwing tip device element 30 across the lower aerodynamic surface 34 ofthe second wing tip device element 30. In this example the first upperwidth 43, the first lower width 44, the second upper width 45, and thesecond lower width 46 each have a dimension of up to approximately 50%of the maximum root thickness of the second wing tip device element 30,such as between 15% and 100% of the maximum root thickness.

The fairing 40 further has a leading edge width 47 extending from theleading edge 36 in a substantially chordwise direction of the secondwing tip device element towards the leading edge 26 of the first wingtip device element 20, and a trailing edge width 48 aft of the trailingedge 35 extending in a substantially chordwise direction of the secondwing tip device element 30 towards the trailing edge 25 of the firstwing tip device element 20. In this example the leading edge width 47and trailing edge width 48 are up to approximately 50% of the maximumroot thickness of the second wing tip device element 30, such as between15% and 100% of the maximum root thickness.

In a second example shown in FIG. 8, the fairing 40 extends from thetrailing edge 35 of the second wing tip device element 30 up to andabutting the trailing edge 25 of the first wing tip device element 20.As in previous examples, the fairing 40 envelopes the junction betweenthe second wing tip device element 30 and the first wing tip deviceelement 20 to hide the junction from the airflow. The first upper width43, first lower width 44, second upper width 45, second lower width 46,and leading edge width 47 of the fairing 40 are all substantiallyconstant around the fairing 40, however the trailing edge width 48extends to the trailing edge 25 of the first wing tip device element 20(See FIG. 8b ).

In a third example, shown in FIG. 9, the fairing 40 extends aft of thetrailing edge 25 of the first wing tip device element 20. The firstupper width 43, first lower width 44, second upper width 45, and secondlower width 46 are all substantially constant from the leading edge 36of the second wing tip device element 30 to a transition point 51approximately 60% of the chord length of the second wing tip deviceelement 30 aft of the leading edge 36 of the second wing tip deviceelement 30. Rearward of the transition point 51 is a transition region52 in which the second upper width 45 and second lower width 46 increaseup to the trailing edge 35 of the second wing tip device element 30. Thefairing 40 extends aft of the trailing edge 35 of the second wing tipdevice element 30 and the trailing edge 25 of the first wing tip deviceelement 20 towards a cusp 55 of the fairing 40. The cusp 55 projects inthe substantially chordwise direction of the second wing tip deviceelement 30 from the second wing tip device element 30.

In a fourth example, shown in FIG. 10, the rearward extending fairing 40provides an attachment position for avionic systems 60, such as alanding light or antenna.

In a fifth example, shown in FIG. 11, the fairing 40 extends aft of thetrailing edge 35 of the second wing tip device element 30 but does notextend forward of the leading edge 36 of the second wing tip deviceelement 30. Instead the widths 43, 44, 45, 46 of the fairing 40gradually decrease forward of a transition point 51 towards atermination point 53 positioned at a distance approximately 50% of thechord length of the second wing tip device element 30 from the trailingedge 35 of the second wing tip device element 30, such as between 5% and100% of the chord length of the second wing tip device element 30 fromthe trailing edge 35 of the second wing tip device element 30. Thefairing 40 therefore does not extend forward of the termination point53, and the junction between the first wing tip device element 20 andsecond wing tip device element 30 forward of this termination point 53is exposed to the airflow.

The interference effects from the adverse pressure gradients of thefirst wing tip device element 20 and second wing tip device element 30begin towards the leading edge of the junction, and develop along thejunction towards the trailing edge of the junction. It may therefore bethe case that the interference effects are minimal forward of thecertain point, and a fairing 40 is not required along the entirejunction. Hence a localised fairing 40, i.e. a fairing that does notextend forward of a termination point 53, can be used to reduce theinterference drag near the rear of the junction where the interferenceeffects are most severe.

It will be clear to the skilled person that the examples described abovemay be adjusted in various ways. For instance, FIG. 12 shows an examplein which the first upper width 43, first lower width 44, second upperwidth 45 and second lower width 46 each vary independently in size alongthe chord length between the trailing edge 35 and leading edge 36 of thesecond wing tip device element 30.

The fairing 40 may extend adjacent the upper aerodynamic surface 33 andlower aerodynamic surface 34 of the second wing tip device element 30,as in previous examples, or may extend adjacent only one of the upperaerodynamic surface 33 and lower aerodynamic surface 34. For instance,in FIG. 13 an example is shown in cross-section in which the fairing 40extends adjacent the upper aerodynamic surface 33 of the second wing tipdevice element 30 but not the lower aerodynamic surface 34. FIG. 14shows an example in cross-section in which the fairing 40 extendsadjacent the lower aerodynamic surface 34 of the second wing tip deviceelement 30 but no the upper aerodynamic surface 33.

It will be clear to the skilled person that the invention is equallyapplicable to reduce interference effects between other types of splitwinglets.

For instance, FIGS. 15 & 16 show examples of the wing tip device 12 inwhich similar reference numerals are used to denote similar parts butnumbered in the 100 series. In the example of FIG. 15, the first wingtip device element 120 is a downwardly extending wing tip device elementand the second wing tip device element 130 is an upwardly extending wingtip device element, such that the root end 131 of the second wing tipdevice element 130 attaches to the upper aerodynamic surface 123 of thefirst wing tip device element 120. The fairing 140 extends along theupper aerodynamic surface 133 and lower aerodynamic surface 134 of thesecond wing tip device element 130, but may alternatively extend acrossonly the lower aerodynamic surface 134, or may extend across only thelower aerodynamic surface as shown in FIG. 16.

It will be clear that many of the features described in relation to eachexample may be varied within the normal activity of the skilled person.For example, the first wing tip device element 20 and second wing tipdevice element 30 may be curved or straight. The first and second wingtip device elements 20, 30 could both be upwardly extending, downwardlyextending, or one of the wing tip device elements could extend in aspanwise direction in the plane of the wing (i.e. at a cant angle of 0).

The fairing 40 may wrap entirely around the junction between the firstand second wing tip device elements 20, 30, or the fairing may onlyextend up to a termination point 53 between the trailing edge 35 andleading edge 36 of the second wing tip device element. The fairing mayhave a first termination point on the upper aerodynamic surface 33 ofthe second wing tip device element and a second termination point on thelower aerodynamic surface 34 of the second wing tip device element, andthe first and second termination points may be at different positionsalong the chordwise direction of the second wing tip device element 30.

A rubber seal, or sealant, can be placed between the wing tip deviceelements 20, 30 and the fairing 40 in order to improve contouringbetween the respective elements.

The wing tip devices described in each of the above examples can beassembled by attaching the root end of the second wing tip deviceelement to the first wing tip device element at a location outboard ofthe first wing tip device element root end, and attaching the fairingbetween the first and second wing tip device elements, wherein thefairing extends aft from the second wing tip device element trailingedge.

The fairing may be smoothly blended into the second wing tip deviceelement to enable assembly of the fairing and second wing tip deviceelement as a single moulding.

The wing tip devices may be fitted, or retro-fitted, to the outboard endof an aircraft having either no wing tip device (in the case of‘fitting’) or as a replacement for an existing wing tip device (in thecase of ‘retro-fitting’).

Where the word ‘or’ appears this is to be construed to mean ‘and/or’such that items referred to are not necessarily mutually exclusive andmay be used in any appropriate combination.

Although the invention has been described above with reference to one ormore preferred embodiments, it will be appreciated that various changesor modifications may be made without departing from the scope of theinvention as defined in the appended claims.

The invention is:
 1. A wing tip device comprising: a first wing tipdevice element for attaching at a first wing tip device element root toa tip of an aircraft wing; a second wing tip device element extendingfrom a second wing tip device element root to a second wing tip deviceelement tip, the second wing tip device element root is outboard, whenviewed in a wing planform direction, of the first wing tip deviceelement root, wherein the first wing tip device element includes a firstwing tip device element leading edge and a first wing tip device elementtrailing edge, and the second wing tip device element includes a secondwing tip device element leading edge and a second wing tip deviceelement trailing edge; and a fairing between the first and second wingtip device element extending aft from the second wing tip device elementtrailing edge.
 2. The wing tip device according to claim 1, wherein thesecond wing tip device element trailing edge is forward of the firstwing tip device element trailing edge.
 3. The wing tip device accordingto claim 2, wherein the fairing extends to the first wing tip deviceelement trailing edge.
 4. The wing tip device according to claim 1,wherein the fairing extends aft of the first wing tip device elementtrailing edge.
 5. The wing tip device according to claim 1, wherein thefairing is separable from the first wing tip device element and/orsecond wing tip device element.
 6. The wing tip device according toclaim 1, wherein the fairing is integrally formed with the second wingtip device element.
 7. The wing tip device according to claim 1,including a vertex between the second wing tip device element and thefirst wing tip device element, when viewed in the aircraft longitudinaldirection, the vertex having an angle of less than 120 degrees.
 8. Thewing tip device according to claim 1, wherein the fairing has a widthextending across the first wing tip device element in a direction of athickness of the second wing tip device element, and wherein the widthis at least 15% of the root thickness of the second wing tip deviceelement and/or no more than 100% of the root thickness of the secondwing tip device element.
 9. The wing tip device according to claim 1,wherein the first wing tip device element has a wetted area and thesecond wing tip device element has a wetted area, and wherein the wettedarea of the second wing tip device element is larger than the wettedarea of the first wing tip device element.
 10. The wing tip deviceaccording to claim 9, wherein the wetted area of the second wing tipdevice element is less than 20% of the wetted area of the first wing tipdevice element.
 11. The wing tip device according to claim 1, whereinthe fairing extends towards the leading edge of the second wing tipdevice element along an upper aerodynamic surface and/or a loweraerodynamic surface of the second wing tip device element.
 12. The wingtip device according to claim 11, wherein the fairing extends around theleading edge of the second wing tip device between the upper and loweraerodynamic surface areas.
 13. The wing tip device according to claim 4,wherein an avionic system or light is attached to the fairing at aposition aft of the first wing tip device element trailing edge.
 14. Thewing tip device according to claim 1, wherein the first wing tip deviceelement is an upwardly extending wing tip device element.
 15. The wingtip device according to claim 1, wherein the second wing tip deviceelement is a downwardly extending wing tip device element.
 16. The wingtip device according to claim 1, wherein the fairing forms an angle oless than 40 degrees to the first and/or second wing tip device elementat an intersection of the fairing to the respective wing tip deviceelement.
 17. The wing tip device according to claim 1, wherein thefairing has a concave outer surface, when viewed in the aircraftlongitudinal direction, between the first wing tip device element andsecond wing tip device element.
 18. The wing tip device according toclaim 1, wherein the fairing encloses a hollow volume.
 19. The wing tipdevice according to claim 1, wherein one or more fasteners are disposedbetween the fairing and the first wing tip device element or second wingtip device element.
 20. The wing tip device according to claim 1,wherein the second wing tip device element root is attached at ajunction to the first wing tip device element outboard, when viewed inthe wing planform direction, of the first wing tip device element root;and wherein the second wing tip device element trailing edge is forwardof the first wing tip device element trailing edge at the junction. 21.An aircraft wing assembly comprising: a fixed wing including a fixedwing root attached to a fuselage of an aircraft, a fixed wing tip at anend of the fixed wing opposite to the root; a first wing tip deviceelement including a first root, a first tip, a first leading edge, afirst trailing edge and a first skin spanning the first leading edge andthe first trailing edge, wherein the first root is attached to the fixedwing tip and wherein the first leading edge and the first trailing edgeboth span between the first root and the first tip; a second wing tipdevice element including a second root, a second tip, a second leadingedge, a second trailing edge and a skin spanning the second leading andtrailing edges, wherein the second root is attached to the first wingtip device and extends from the first skin at a position on the firstskin outboard of the first root along a wing planform direction; and afairing covering a junction between the first and second wing tipdevices wherein the fairing includes a fairing skin spanning the firstand second skins, and the fairing skin extends from at least the secondleading edge to aft of the second trailing edge.
 22. The aircraft ofclaim 21, wherein the fairing extends aft of the first trailing edge.23. The method of assembling a wing tip device, the wing tip deviceincluding: a first wing tip device element with a first wing tip deviceelement root end for attaching to an aircraft wing and a first wing tipdevice element trailing edge, a second wing tip device element having asecond wing tip device element root end and a second wing tip deviceelement trailing edge, and a fairing; the method comprising the stepsof: attaching the second wing tip device element root end to the firstwing tip device element outboard of the first wing tip device elementroot end, and; attaching the fairing between the first and second wingtip device elements which extends aft from the second wing tip deviceelement trailing edge.
 24. The method according to claim 23, wherein thesecond wing tip device element root end is attached to the first wingtip device element at a junction outboard of the first wing tip deviceelement root end such that the second wing tip device trailing edge isforward of the first wing tip device element trailing edge at thejunction.